/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * kernel/environ/env_removevar.c
 *
 *   Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#ifndef CONFIG_DISABLE_ENVIRON

#include <string.h>
#include <sched.h>

#include "environ/environ.h"

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: env_removevar
 *
 * Description:
 *   Remove the referenced name=value pair from the environment
 *
 * Parameters:
 *   group The task group with the environment containing the name=value pair
 *   pvar A pointer to the name=value pair in the restroom
 *
 * Return Value:
 *   Zero on success
 *
 * Assumptions:
 *   - Not called from an interrupt handler
 *   - Caller has pre-emptions disabled
 *   - Caller will reallocate the environment structure to the correct size
 *
 ****************************************************************************/

int env_removevar(FAR struct task_group_s *group, FAR char *pvar)
{
	FAR char *end;				/* Pointer to the end+1 of the environment */
	int alloc;					/* Size of the allocated environment */
	int ret = ERROR;

	DEBUGASSERT(group && pvar);

	/* Verify that the pointer lies within the environment region */

	alloc = group->tg_envsize;		/* Size of the allocated environment */
	end   = &group->tg_envp[alloc];	/* Pointer to the end+1 of the environment */

	if (pvar >= group->tg_envp && pvar < end) {
		/* Set up for the removal */

		int   len   = strlen(pvar) + 1;	/* Length of name=value string to remove */
		char *src   = &pvar[len];		/* Address of name=value string after */
		char *dest  = pvar;				/* Location to move the next string */
		int   count = end - src;		/* Number of bytes to move (might be zero) */

		/* Move all of the environment strings after the removed one 'down.'
		 * this is inefficient, but robably not high duty.
		 */

		while (count-- > 0) {
			*dest++ = *src++;
		}

		/* Then set to the new allocation size.  The caller is expected to
		 * call realloc at some point but we don't do that here because the
		 * caller may add more stuff to the environment.
		 */

		group->tg_envsize -= len;
		ret = OK;
	}

	return ret;
}

#endif							/* CONFIG_DISABLE_ENVIRON */
